Environmental Entomology最新文献

The western bean cutworm (Striacosta albicosta) is a primary pest of corn and dry edible bean, for which control measures are often warranted. Inundative releases of Trichogramma ostriniae have been used to control lepidopterous pests, such as the European corn borer (Ostrinia nubilalis), in eastern North America (e.g., New York, Virginia). However, no prior field studies have assessed T. ostriniae as a biological control agent in the North American Great Plains. Objectives for this study were (i) to determine the suitability of S. albicosta as a host for T. ostriniae and (ii) to assess the feasibility of T. ostriniae as a biological control agent of S. albicosta in Nebraska corn and dry edible bean fields. Dispersal and parasitism were monitored with yellow sticky cards and sentinel egg masses (O. nubilalis, S. albicosta, and Ephestia kuehniella) at 36 locations surrounding a central release point. Trichogramma ostriniae adults tended to be concentrated near the point of release. However, egg parasitism was so low that the minimum rates of T. ostriniae needed for effective control could not be determined. Our evidence indicates that the low parasitism measured in this study may indicate low suitability of T. ostriniae to Western Nebraska and, possibly, the Great Plains.

The foxglove aphid, Aulacorthum solani (Kaltenbach), is a polyphagous economic pest. In this study, A. solani were fed on detached leaves of dockleaf knotweed, Persicaria lapathifolia (L.) Delarbre. Survival, development, and reproduction were studied at constant temperatures of 17, 20, 23, 26, 29, and 32 °C. These data were compared with those of controls fed on Glycines max (L.) Merrill. At 17, 20, 23, and 26 °C, the survival rate of A. solani adults fed on P. lapathifolia were lower than those fed on G. max; the adult longevity, aphid total longevity, and reproduction period were shorter. At 20, 23, and 26 °C, the adult fecundity, intrinsic rate of increase, finite rate of increase, and net reproductive rate of A. solani fed on P. lapathifolia were smaller than those fed on G. max. At 29 °C, the survival rate of A. solani adults fed on P. lapathifolia were higher than those fed on G. max; the adult longevity and aphid total longevity were longer. These results are consistent with our finding that A. solani feed on P. lapathifolia, which is important for studying the host adaptability of A. solani.

Many countries operate continuous trapping programs to detect invasive fruit flies (Diptera: Tephritidae) that threaten fruit and vegetable production. Food-based attractants are an important component of these programs, as they are generalized baits that attract both sexes of all target species. However, food baits are considered weak attractants, and the development of improved food attractants would benefit surveillance efforts. Prior work on protein bait sprays demonstrated that the addition of ammonium acetate increased their attractiveness to tephritid fruit flies, and the present study was conducted to determine whether adding ammonium acetate to torula yeast borax solution (a commonly used food bait) similarly increased its attractiveness. Four field experiments were performed in Hawaii comparing captures of Ceratitis capitata (Wiedemann), Bactrocera dorsalis (Hendel), and Zeugodacus cucurbitae (Coquillett) in Multilure traps baited with standard torula yeast borax solution or with the standard solution plus 1% ammonium acetate. Captures of C. capitata and B. dorsalis were significantly higher for the ammonium acetate-supplemented solution, while results for Z. cucurbitae were inconsistent. In one experiment involving only C. capitata, an additional bait having 5% ammonium acetate was included, and captures for both 1% and 5% ammonium acetate exceeded the standard solution but did not differ from one another. Sex ratios of captured flies were similar between food baits for all three species. These results are compared with similar studies on Anastrepha spp., and implications for surveillance programs are discussed.

The microbial composition of insect guts is typically influenced by the type of food consumed, and conversely, these microbes influence the food habits of insects. Western flower thrips (WFT; Frankliniella occidentalis) is an invasive pest with a wide range of hosts, including vegetables and horticultural crops. To elucidate variations in gut bacteria among WFT feeding on rose (Rosa rugosa) flowers (FF), kidney bean (Phaseolus vulgaris) pods (PF), and kidney bean leaves (LF), we collected adult guts and extracted DNA for 16S ribosomal RNA gene sequencing of microbial communities. The results revealed that the FF population had the highest number of annotations. Alpha diversity analysis revealed that the Chao and Ace indexes were the greatest in the PF population, indicating a higher abundance of gut bacteria. Moreover, the Simpson index was the highest in the FF population, indicating that gut bacterial diversity was the highest in the FF population. Comparison of species composition demonstrated that Proteobacteria dominated all 3 populations at the phylum level, with Actinobacteria being the subdominant phylum. At the genus level, Stenotrophomonas was the dominant bacteria in the PF and LF populations, whereas Rosenbergiella was dominant in the FF population. KEGG pathway annotation predicted that the gut bacteria of adult WFT were mainly involved in carbohydrate and amino acid metabolism. Our results revealed that the diversity and composition of WFT gut microbiota are influenced by diet, offering evidence for future studies on the ecological adaptability of WFT and the mechanisms underlying the interaction between gut microbiota and host.

The eastern larch beetle, Dendroctonus simplex LeConte, is a North American species of bark beetle that shares the distribution of its host, Larix laricina (Du Roi) K. Koch. A recent outbreak in the Great Lakes region has prompted renewed interest in the chemical ecology of eastern larch beetle and its natural enemies. Here, we describe field assays elucidating these insects' flight responses to host resin odors and pheromone components in Minnesota and laboratory olfactometer assays illustrating walking responses by eastern larch beetle to pheromone components produced by female beetles. In field trials, the addition of host monoterpenes ∆-3-carene and α-pinene to seudenol lures increased trap captures of eastern larch beetles. Similarly, α-pinene increased captures of Thanasimus spp. predators in seudenol-baited funnel traps. Frontalin release rates between 0.014-3.3 mg/day did not significantly alter catches of eastern larch beetles with seudenol alone, however, still higher concentrations of frontalin (24 mg/day) decreased catches. In contrast, increasing frontalin release rates increased attraction of Thanasimus spp. to seudenol. In a laboratory olfactometer assay, a combination of frontalin and seudenol released at rates comparable to those of a solitary, mining female arrested walking male eastern larch beetles whereas either compound alone did not. Insights into the eastern larch beetle's chemical ecology will improve understanding of cues in host and mate location that may be exploited for management.

Pesticides released into the environment are increasingly recognized as a global threat to freshwater ecosystems because of their adverse effects on non-target organisms, particularly aquatic insects and other arthropods. Superoxide dismutases (SODs) are important antioxidant enzymes that play a crucial role in protecting organisms from oxidative stress induced by harmful materials. In this study, we identified 2 cellular SODs (PxSOD1 and PxSOD2) in Protohermes xanthodes Navás (Megaloptera: Corydalidae), an freshwater predatory insect, and determined the oxidative stress induced in P. xanthodes larvae by sublethal exposure to chlorpyrifos (CPF). PxSOD1 and PxSOD2 are members of the cytoplasmic Cu/ZnSODs and mitochondrial MnSODs, respectively, and differ substantially in protein structure. Both PxSOD1 and PxSOD2 recombinant proteins demonstrated catalytic activity toward O2•- in the activity assays. After exposure to sublethal concentrations of CPF, malondialdehyde (MDA) content and SOD activities were increased in P. xanthodes larvae in a dose-dependent manner. PxSOD1 expression was decreased in the 0.42 and 4.2 μg/L CPF groups and increased in the 4.2 μg/L CPF group. PxSOD2 was upregulated by 0.42, 4.2, and 8.4 μg/L CPF treatments and the expression levels in the 4.2 and 8.4 μg/L CPF groups were significantly higher than that in the no CPF control. Our results suggest that sublethal concentrations of CPF can induce oxidative stress in P. xanthodes larvae, and the cellular SODs in P. xanthodes larvae may contribute to the protection against CPF-induced oxidative stress.

Colonizing aphids play an important role in the transmission of RNA phytoviruses in the family Solemoviridae. According to "host manipulation hypothesis," phloem limited and persistently transmitted Solemoviridae viruses modulate host physiology that positively affects vector behavior and fitness and facilitates virus spread. However, it is unclear if virus-modulated host effects on vectors across pathosystems involving Solemoviridae members are always positive. Cotton leafroll dwarf virus (CLRDV) is a recently introduced Solemoviridae member in the United States, and it is transmitted by the cotton aphid (Aphis gossypii). Effects of CLRDV infection on vector behavior and fitness were evaluated on its primary host plant, cotton (Gossypium hirsutum), and an alternate host plant, hibiscus (Hibiscus acetosella). In this study, changes to viruliferous and non-viruliferous aphid preference and aphid fitness on virus-infected and non-infected hosts were examined. In contrast to the hypothesized preference of non-viruliferous aphids for infected plants and vice-versa, both viruliferous and non-viruliferous A. gossypii preferred non-infected cotton and hibiscus plants over CLRDV-infected plants. This suggested that the preference of non-viruliferous vectors to non-infected plants might negatively impact virus acquisition, whereas the preference of viruliferous vectors toward non-infected plants could positively facilitate virus inoculation. The total fecundity and intrinsic rate of increase of aphids were higher on non-infected plants compared with CLRDV-infected plants. The lack of enhanced fitness benefits on CLRDV-infected hosts also could negatively impact virus spread. Overall, this study suggested that "host manipulation hypothesis" favoring vector attraction and enhanced fitness on infected plants does not apply to all pathosystems involving Solemoviridae members.

Nectar is an important source of food for adult mosquitoes, influencing their biological characteristics including longevity, fecundity, and flight range. Consequently, it can impact mosquitoes' survival and efficiency in transmitting disease. Different mosquito species are known to show preferences for flower nectar from certain plants, yet despite the importance of these plant-mosquito associations, knowledge of such biotic interactions is sparse. Here, we present a systematic map to address the question: "Which nectar do mosquitoes feed on?." The mapping process identified 49 articles (comprising 51 studies) meeting inclusion criteria, detailing 397 records of 74 mosquito species feeding on nectar from 145 plant species and 109 genera. Data extracted from the map were then analyzed to better understand if mosquitoes showed preferences for specific plant nectar. A key finding from this study is clear evidence supporting the hypothesis that mosquitoes exhibit preferences for nectar from particular plant species, including 77 species of plants and 58 genera for Aedes species, 18 species of plants and 17 genera for Anopheles species, and 16 species of plants and 16 genera for Culex species (all 3 genera belong in Diptera: Culicidae). Our study also highlighted the need for further field and laboratory work in time and space and using methods that randomly selects plant species for investigation. This would facilitate a better understanding of the relationship between mosquito feeding behavior and nectar seasonality and abundance; data that are critical for the development and improvement of new mosquito control methods to tackle vector-borne diseases.

Corn earworm, Helicoverpa zea Boddie (Lepidoptera: Noctuidae), is a common herbivore that causes economic damage to agronomic and specialty crops across North America. The interannual abundance of H. zea is closely linked to climactic variables that influence overwintering survival, as well as within-season host plant availability that drives generational population increases. Although the abiotic and biotic drivers of H. zea populations have been well documented, prior temporal H. zea modeling studies have largely focused on mechanistic/simulation approaches, long term distribution characterization, or degree day-based phenology within the growing season. While these modeling approaches provide insight into H. zea population ecology, growers remain interested in approaches that forecast the interannual magnitude of moth flights which is a key knowledge gap limiting early warning before crops are planted. Our study used trap data from 48 site-by-year combinations distributed across North Carolina between 2008 and 2021 to forecast H. zea abundance in advance of the growing season. To do this, meteorological data from weather stations were combined with crop and soil data to create predictor variables for a random forest H. zea forecasting model. Overall model performance was strong (R2 = 0.92, RMSE = 350) and demonstrates a first step toward development of contemporary model-based forecasting tools that enable proactive approaches in support of integrated pest management plans. Similar methods could be applied at a larger spatial extent by leveraging national gridded climate and crop data paired with trap counts to expand forecasting models throughout the H. zea overwintering range.

Herbivorous insects utilize olfactory and visual cues to orient on suitable host plants, and such cues can be employed to facilitate insect monitoring. Lygus lineolaris Palisot de Beauvois is a polyphagous pest throughout North America. Monitoring this pest as it moves between crop and non-crop hosts remains challenging, and a lack of effective monitoring tools complicates management of this insect. In this study, we examined the electrophysiological and behavioral responses of L. lineolaris to the volatile emissions of 2 crop hosts: alfalfa and strawberry. Gas chromatography with electroantennographic detection was applied to identify antennally active compounds in headspace extracts of flowering host plants, before responses to individual compounds were examined in the field. Five compounds consistently elicited antennal depolarizations in adults of L. lineolaris and, of these, (±)-linalool increased the capture rate of L. lineolaris females in the field. Subsequent experiments examined the influence of visual cues and stereochemistry on capture rate, revealing that lures containing (±)-linalool and (S)-(+)-linalool significantly increased the capture rate of L. lineolaris females compared with traps baited with (R)-(-)-linalool and controls, indicating that L. lineolaris is attracted to (S)-(+)-linalool. While lures increased capture on red traps, this was not the case for white traps, emphasizing the importance of visual cues in the movements and monitoring of L. lineolaris. This study demonstrates that L. lineolaris is attracted to (S)-(+)-linalool in the field, and that attraction depends on trap color. This knowledge is expected to improve monitoring strategies for L. lineolaris in agricultural systems.